title: p53 and cell cycle independent dysregulation of autophagy in chronic lymphocytic leukaemia.
abstract: BACKGROUND
  Activation of wild-type p53 with the small molecule sirtuin inhibitor Tenovin-6 (Tnv-6) induces p53-dependent apoptosis in many malignant cells. In contrast, Tnv-6 reduces chronic lymphocytic leukaemia (CLL) cell viability with dysregulation of autophagy, without increasing p53-pathway activity.
  
  
  METHODS
  Here, we have investigated whether a quiescent phenotype (unique to CLL) determines the Tnv-6 response, by comparing the effects of Tnv-6 on activated and proliferating CLL. We further studied if these responses are p53-dependent.
  
  
  RESULTS
  Unlike quiescent cells, cell death in activated cultures treated with Tnv-6 was consistently associated with p53 upregulation. However, p53 acetylation remained unchanged, without caspase-3 cleavage or apoptosis on electron microscopy. Instead, cellular ultrastructure and protein profiles indicated autophagy inhibition, with reduced ubiquitin-proteasome activity. In specimens with mutant TP53 cultured with Tnv-6, changes in the autophagy-associated protein LC3 occurred independently of p53. Cells treated with Tnv-6 analogues lacking sirtuin inhibitory activity had attenuated LC3 lipidation compared with Tnv-6 (P0.01), suggesting that autophagy dysregulation occurs predominantly through an effect on sirtuins.
  
  
  CONCLUSIONS
  These cell cycle and p53-independent anti-leukaemic mechanisms potentially offer novel therapeutic approaches to target leukaemia-sustaining cells in CLL, including in disease with p53-pathway dysfunction. Whether targets in addition to sirtuins contribute to autophagy dysregulation by Tnv-6, requires further investigation.
authors.affiliation: Dundee Cancer Centre, Ninewells Hospital, University of Dundee, Dundee, Scotland DD1 9SY, UK.
authors.forename: M J
authors.initials: MJ
authors.lastname: Groves
authors.forename: C E
authors.initials: CE
authors.lastname: Johnson
authors.forename: J
authors.initials: J
authors.lastname: James
authors.forename: A R
authors.initials: AR
authors.lastname: Prescott
authors.forename: J
authors.initials: J
authors.lastname: Cunningham
authors.forename: S
authors.initials: S
authors.lastname: Haydock
authors.forename: C
authors.initials: C
authors.lastname: Pepper
authors.forename: C
authors.initials: C
authors.lastname: Fegan
authors.forename: L
authors.initials: L
authors.lastname: Pirrie
authors.forename: N J
authors.initials: NJ
authors.lastname: Westwood
authors.forename: P J
authors.initials: PJ
authors.lastname: Coates
authors.forename: I G
authors.initials: IG
authors.lastname: Ganley
authors.forename: S
authors.initials: S
authors.lastname: Tauro
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D001343:Autophagy / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D001549:Benzamides / Q000494:pharmacology; D053148:Caspase 3 / Q000235:genetics; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D049109:Cell Proliferation / Q000187:drug effects; D006801:Humans; D007376:Interleukin-2 / Q000494:pharmacology; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D008869:Microtubule-Associated Proteins / Q000235:genetics; D008875:Middle Aged; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: D001549:Benzamides; D007376:Interleukin-2; C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D025801:Ubiquitin; C574854:tenovin-6; D053148:Caspase 3; D046988:Proteasome Endopeptidase Complex